By Annie Barrett
June 10, 2009 at 03:54 PM EDT

In the midst of an eight-night run performing in London’s O2 Arena, Britney Spears announced another round of dates for 2009’s top-grossing concert tour. Circus will return to North America beginning August 20, and will hit 20 cities in the U.S. and Canada including New York, Boston, Philadelphia, Chicago, and Los Angeles. She’ll end the wild ride September 27 in Las Vegas. Tickets for the new dates go on sale Friday, June 19.

Earlier: Britney Spears to tour Australia